For instance, in a process of fabricating a semiconductor device, a predetermined circuit pattern is formed on a semiconductor wafer by using the photolithography technology. According to this photolithography process, a resist film is formed on a wafer, the resist film is exposed in a predetermined pattern, and then the exposed wafer is developed, whereby the circuit pattern is formed thereon.
As a method of forming a resist film on a wafer, so-called spin coating is widely used, which supplies a predetermined amount of a resist liquid is supplied to the center portion of a wafer held substantially horizontally and then rotates the wafer at a high speed so as to spread the resist liquid over the entire wafer surface.
Unexamined Japanese Patent Application KOKAI Publication No. 2001-189266, for example, discloses, as an apparatus which forms a film by such spin coating, a coating process apparatus which comprises a process cup so laid out as to surround a wafer and coercively exhausts the atmosphere around the wafer by carrying out coercive exhausting from the bottom, and an airflow control plate which is so provided as to surround the wafer in atmosphere around the wafer by carrying out coercive exhausting from the bottom, and an airflow control plate which is so provided as to surround the wafer in the process cup and controls an airflow generated around the wafer.
In this coating apparatus, however, as an atmosphere extraction port of a exhaust passage is positioned in the vicinity of an edge face of the wafer, drying of the resist liquid at the peripheral portion of the wafer is accelerated due to an airflow flowing into the exhaust passage. Accordingly, the resist liquid flowing toward the periphery of the wafer from the center thereof is likely to deposit on the periphery of the wafer, so that the resist film becomes thicker at the peripheral portion of the wafer than at the center portion.
Recently, as miniaturization of circuit patterns and high integration are advanced, a resist film to be formed becomes thinner and such a slight unevenness of the thickness of a resist film largely affects the yield and the quality of a product.